In manufacturing processes, particularly those involving production assembly lines, it is often necessary for an operator to turn on an industrial machine such as a punch press, welding device, or the like at given time intervals. Normally, these machines are energized by a pushbutton and in order to maintain certain type of machines in an energized state, it is necessary for an operator to maintain a physical pressure on the pushbutton to hold it closed. This back pressure on the button may be substantial and the operator will often have to use his fingers as well as thumb in applying a gripping action to provide sufficient thumb pressure on the button.
In such operations as the foregoing, an operator may turn an industrial machine on and off several hundred times during a single shift. It is not uncommon, as a consequence, for the operator to develop an afflication known as carpal tunnel syndrome. Essentially, the repetitive motion results in an enlargement of the tendons from the fingers and thumb within a protective sheath. As a consequence, there is pressure placed on nerves located adjacent to the sheath resulting in a tingling and numbness sensation of the thumb and the first three fingers. Essentially, the result is that the operator loses his grasping strength.
Many industrial machines are provided with two switches both of which must be operated in order to start the machine. These switches are physically separated by a distance such that the operator must use both hands or thumbs to actuate the same simultaneously. The purpose for such a dual switch arrangement is to provide a safety feature in that the operator cannot inadvertently damage one hand or arm while turning the machine on with the other. In other words, by requiring the use of both arms and hands to turn on the machine, the operator's arms cannot be damaged by the machine. In such instances where two switches are used, then the carpal tunnel syndrome could develop in both hands of an operator.
While it is known in the prior art to provide switches for industrial equipment at spaced locations so as to meet the safety feature of requiring both hands of the operator to energize the equipment as mentioned above, and further while switches can be designed to operate relays which will ease the back pressure on a switch button, there has not been available any really effective solution to the carpal tunnel syndrom development in workers who operate such machines.
Examples of separated switches for safety purposes and relay operated switches are shown in prior U.S. Pat. Nos. 4,074,602 and 4,054,935 respectively.